What's growing from your mop??

Yes, that's a mushroom, growing from my MOP.  In the morning I noticed there was something on the mop that I didn't think I had seen before.  Then I came home - about 10 hours later - and this is what I found.  I was soooooooo grossed out.  Instead of throwing the mop out my 21st floor window I carried it to the stairwell where I knew it would disappear eventually.  EWW!

I discussed my mop with a friend and a little while later he emailed me this picture from a Chinese website.

Is it a normal thing in China to have mushrooms growing out of mops??  I just thought it was my mop but apparently it happens.  YUCK.  I am never using regular mops again!